JPS586322B2 - Integrated circuit with thermal feedback in mind - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated circuit having a differential input stage and an output stage with an alternating heat source, e.g. class B push-pull configuration, on the same chip.

There is a problem of thermal feedback in this type of integrated circuit, and as a countermeasure, there are methods to place the differential elements of the differential input stage in a thermally balanced position with respect to the heat source, and methods to maintain a sufficient distance between the input stage and the heat source. be.

However, in the former method, when there are multiple heat sources, they are placed at the minimum point that integrates their heat feedback effects, and this alone often does not provide satisfactory performance.

Therefore, the former and the latter are generally used in combination to suppress the thermal feedback effect below a certain value, but the latter method generally has the drawback that the required distance is considerably large, increasing the size of the semiconductor pellet.

Therefore, the present applicant previously proposed the circuit and arrangement shown in FIGS. 1 and 2.

That is, diodes 113 and 114 are provided at the emitters of differential transistors 111 and 112, and these are arranged so that the influence of heat generated from output transistors 121 and 122 becomes the same common-mode component on both differential inputs. .

According to this, there is an effect that heat feedback can be reduced without increasing the size of the pellet, in other words, the distance between the differential input stage and the output stage.

However, since this circuit has diodes 113 and 114 connected to the emitters of differential transistors 111 and 112, the voltage between the input terminals increases by the rising voltage of the diodes, which is disadvantageous in terms of voltage reduction.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an excellent method for reducing voltage, which can reduce the feedback effect without increasing the size of the semiconductor pellet.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic circuit diagram showing an embodiment of the present invention, and FIG. 4 is a layout diagram of the circuit components.

In these figures, 100 is an input stage 110 with a differential configuration.
and an integrated circuit having an output stage 120, 111,
111', 112, and 112' are first-stage differential amplification transistors of the input stage 110, and the transistors 111 and 111' and 112 and 112' are connected in a differential series, respectively.
Transistors 111, 111' and 112, 112' are configured differentially.

121 and 122 are output transistors of the output stage 120 having a class B push-pull configuration.

And these pairs of differential transistors 111, 111',
and 112, 112' and output transistor 121, 1
22 are arranged as shown in FIG. 4 or 5.

That is, the input differential transistor circuit 110 and the output transistor circuit 120 are arranged facing each other with a certain distance L, for example, about 1000 μm, and the four differential transistors 111, 111 of the differential transistor circuit 110
', 112, 112' are transistors 111, 111
', 112, 112' are arranged symmetrically so that the influence from the heat source 120 is as follows: transistor 111+transistor 111'=transistor 112+transistor 112'.

With this arrangement, the distances a and d from the output transistor 121 to the differential transistors 111 and 111' are
The sum a+d is equal to the sum of the distances c and b to the differential transistors 112 and 112'.

This also applies when viewed from the output transistor 122.

Therefore, in this case, the output transistor 121 or 12
2 has the same thermal effect on the differential pair input composed of the differential transistors 111, 111' and the differential transistors 112, 112', and the inputs are the same in phase and do not appear at the output terminal. In the circuit configuration shown in FIG. 3, differential transistors 111, 111', 112, 11
2' collector current Ic is Ic=A(expBVbe-1) (1) (where A and B are constants), and its base-emitter voltage Vb
Due to a very small change in e, △Vbe, the collector current Ic
If the influence on is △■c, then by differentiating equation (1), we get (
2) Equation becomes.

△Ic=ABIc・△vbe...(2) Here, △Vbe is the change in Vbe due to thermal feedback, and △
I is the change in Ic caused by this.

Therefore, the differential transistors 111, 111', 1 in FIG.
The amount of heat feedback received by 12 and 112' is △Vbc4v, respectively.
△Vbe2, △Vbe3, △Vbe4, △Iclg
If △1c2, △Ic3, △Ic4 are the resulting changes in Ic, the four differential transistors 111, 111'
, 112, 112' as △vbe1 (transistor 111
) + △Vbe3 (transistor 111') = △Vbe2
(Transistor 112) + △Vbe4 (Transistor 1
12'), △Ic1 (transistor 111) + △Ic3 (transistor 111')
)=ΔIc2 (transistor 112)+Δ■c4 (transistor 112'), and the differential output can be made zero.

FIG. 4 is a characteristic diagram showing the amount of feedback due to heat, with the horizontal axis representing the frequency Hz and the vertical axis representing the input/output signal ratio dB.
A is a characteristic curve based on the circuit configuration and component placement of the present invention, and B is a characteristic curve based on the conventional circuit configuration and component placement.

From this characteristic diagram, it can be seen that the amount of feedback in the present invention is smaller than that in the prior art, and its influence is small.

According to the present invention as described above, it is possible to achieve the same or better effect without increasing the distance between the input stage and the output stage to prevent heat feedback as in the past, and the pellet area can be made smaller than before. .

Further, according to the present invention, since no diode is connected to the emitter of the input stage transistor, it is advantageous in terms of voltage reduction.

[Brief explanation of drawings]

Fig. 1 is a schematic circuit diagram in which a part of the conventional input section and output section circuit is extracted, Fig. 2 is a layout diagram of the components, and Fig. 3 is a schematic diagram of the input section and output section of the high gain amplifier of the present invention. FIG. 4 is a schematic circuit diagram in which a part of the circuit is extracted, FIG. 4 is a layout diagram of its components, FIG. 5 is a layout diagram of input part components of the present invention, and FIG. 6 is a characteristic curve diagram for explaining the present invention. be. 110...Input stage, 120...Output stage, 111,1
11', 112, 112', 121, 122...transistor.

Claims (1)

[Claims] 1 In an integrated circuit having a differential input stage and at least two or more heat sources in the same chip, the differential input stage is composed of at least two or more parallel transistor pairs A, C, ... and B, D, ... Each transistor A, C,...
and B, D... and the first heat source of each of these transistors are respectively a, c... and b, d, and the second
The distances from the heat source to the heat source are respectively a', c'... and b/,
When d/, a+c+...=b+d+..., and a'
The above transistors A, so as to satisfy the relationship +d'+...
B, C, D, ... and the above-mentioned first and second heat sources are arranged and configured in the same manner so that the amount of heat feedback from each of the plurality of heat sources is equal between the positive and negative inputs of the differential input stage. An integrated circuit that takes thermal feedback into consideration, characterized in that it is arranged in a.